Does the Commodore 128 Have a Built-In Clock Calendar?

The Commodore 128 is a versatile machine, but its timekeeping hardware often causes confusion among retro computing enthusiasts. This article provides a definitive answer regarding the presence of a built-in clock calendar, details the specific capabilities of the internal timer chips, and discusses how users managed timekeeping tasks without a battery-backed real-time clock.

Internal Timer Chips

The Commodore 128 motherboard features two Complex Interface Adapter (CIA) chips. These chips include time-of-day registers that can track hours, minutes, seconds, and tenths of seconds while the computer is powered on. However, these timers rely on volatile memory. Once the system is turned off or unplugged, the time data is lost immediately because there is no auxiliary power source to maintain the registers.

Lack of Battery Backup

Unlike some business-oriented computers from the same era, the standard Commodore 128 does not include a battery-backed real-time clock (RTC) circuit. There is no lithium battery or capacitor on the main board designed to keep a calendar running during power outages. Consequently, the system cannot retain the date or time between sessions without external assistance or specific cartridge expansions.

Solutions for Timekeeping

To maintain a persistent clock calendar, users typically relied on third-party expansions. Cartridges containing RTC chips were popular additions that plugged into the expansion port to provide continuous time tracking. Additionally, software solutions existed that prompted users to enter the time at every boot, or some users utilized REU expansions with specific firmware that offered timekeeping features. For most standard operations, however, the base unit requires manual time entry upon each startup.